Here’s the thing: players are going to play the cards they think are most likely to help them win the most against the matchups they expect to see. That’s how competitive games work. If we simply put the good cards of today on the list, then tomorrow rational actors will attempt to substitute the next highest VAR card, or if none can be found, then you keep using it (hello Astro / Clone Chip), paying the tax by switching to a slightly less optimal card somewhere else. In the Internet era, especially with a game focused on networked communications, it’s silly to think that consensus won’t be formed around a replacement set of cards (and tactics) pretty rapidly.
If “is used in too many of the top decks” is the dominant criteria for inclusion in the MWL, then we will eventually arrive at all of the good cards being on the list.
If the card is simply too powerful, rebalance it using mechanisms already present on the card, i.e. if it is too good out of faction, increase the influence cost. If there is a combination of cards that is simply too powerful, but in isolation the pieces are fine, restrict them.